The radio interface is unique to wireless communication systems and is responsible for much of the complexity associated with these systems. The radio communication channel is affected by large and small-scale fading phenomena. The large-scale phenomena are due to the attenuation of the transmitted signal as it travels through the atmosphere. The small-scale effects depend on multipath propagation due to reflections, diffraction and scattering, and behave unpredictably, leading to sharp and quick variations of the signal strength over small distances.
Therefore, it would advantageous to have a receiver system that is able to compensate for the effects of large and small-scale fading phenomena.